As the popularity of the Internet has increased, so has the prevalence of social networking websites and applications. Generally speaking, a social network refers to an application or service that facilitates the building of online communities of people who share interests and activities, or who are interested in exploring the interests and activities of others. Many social network services are web-based and provide a variety of ways for users to interact, such as e-mail and instant messaging services.
In many social networks, a particular user may allow their social contacts to view various actions taken by the particular user. As an example, the user may use a social bookmarking web service to perform the action of bookmarking a web Uniform Resource Locator (URL) and tagging it with a descriptive tag. As another example, the user may use a social networking site relating to movies to perform the action of rating and/or reviewing a movie. As a further example, the user may perform the action of writing a review of a product in a personal blog, such as a status update in a social networking application. As yet another example, the user may perform the action of “checking in” to a particular venue.
The user's social contacts may view the user's actions on the social network and may be interested in performing the same or similar actions (e.g., visiting a website tagged by the user in social bookmarking website, purchasing or renting a movie reviewed by the user at the movie-related social networking site, or purchasing a product reviewed on the user's personal blog). Accordingly, the user may be said to have influenced actions performed by his or her social contacts. In a social network, such actions may further propagate to contacts of the user's contacts. Such a user influence pattern may be referred to as “social capital.”